I encountered an expression:
key benefits to using [something]
To my mind the version below would sound more natural:
key benefits of using [something]
Are both versions correct? Is there any difference in meaning?
Well, both do seem to be used, with benefits of being more common than benefits to, and apparently always has been.
However, I think you probably want benefit of here. The OED has this to say about it:
Thinking about the difference between:
It seems like to and of go different directions. A benefit to society is different from enjoying the benefit of society. Similarly, benefit of clergy and benefit to clergy are quite different.
But I also think you are right that some people may use this interchangeably; I do not find anything wrong with either of your two formulations, but if push came to shove, I’d likely opt for the of version.